Journal of Construction Engineering and Management

Identification of research needs in the building sector, and efficient organization of an institutional research effort for their fulfillment, is analyzed. First, the objectives of research in building are enumerated as: (1) Defining standards of performance and methods of measurement of their attainment; (2) exploring methods for attainment of standards at maximum efficiency; and (3) exploring the possibilities for improving performance of systems and compounds. Then the nature of the research process necessary to attain these objectives is explored. Later, methods for identification of research needs are considered, and criteria for determining their priority are suggested. Possible research contribution as identified in the Israeli building sector was divided, in this context, into the following subjects: (1) Generation of basic data; (2) preparation of infrastructure for codes and specifications; (3) development of tools for analysis and design; (4) development of building products; (5) formulation of building policy; and (6) development of managerial procedures. Finally the features of an efficient research organization are reviewed, the most important of which are careful work planning, high quality of work, conformance to time, and budget constraints and good communication with sponsors.

The nature and extent of resource constraints on projects in developing countries are described in the context of the construction of the dolphin at Tagrin Point in Sierra Leone, West Africa. The interplay between what is possible and what is feasible given the constrained resources is considered in terms of various design alternatives. A new type of ship breasting structure evolving from the construction constraints proves to be functional and promising. The segmental, post‐tensioned dolphin not only meets the structural and functional requirements but, in making use of appropriate modern technologies, resolved the constructional problems on this project and in so doing, opens up a new field in the design and construction of berthing facilities, with the possibility of changing many concepts and previous constraints.

The site of the 10‐story parking garage contained soft to medium consistency residual silty clays overlying carbonate rock formations. This rock contains numerous solution cavities and fracture zones with angles of dip varying from 30°–75°. The rock surface is extremely variable. Surficial soils were incapable of supporting structural loads and deep foundations including drilled caissons and steel H‐piles were evaluated for support of the structure. The potential for extra costs with caissons and H‐piles due to unpredictable bearing grades indicated these solutions to be unacceptable. Excavation of the residual soils to the surface of rock or minimum required depths for settlement considerations, and replacement with compact structural fill was recommended for building support utilizing shallow spread foundations. An allowable bearing pressure of 8 ksf $(400\mathrm{kN}/m^2)$ was utilized for design. This method provided an economical foundation solution and minimal extra costs to the owner.

In response to the increased risk levels found in today's projects, project participants are attempting to quantify project cost risk. Various detailed and conceptual estimating formats are reviewed and a number of probabilistic estimating methods are introduced. Particular attention is given to the process of matching a suitable probabilistic estimating technique to a specific estimating format. To select an appropriate probabilistic method, an estimator must consider data availability, existing correlations, output data requirements, the form of the, estimating model, and the number of cost elements contained in the model. Existing obstacles to more realistic probabilistic cost estimates are reviewed.

Three methods of measuring the performance of construction crews are described and compared. These are: (1) Work sampling; (2) group timing technique; and (3) five‐minute rating. By gathering data from a time‐lapse film, the three methods can be compared for the same operation. Work sampling is shown to provide important information about the characteristics of delays. Considerable time is lost because of waiting for materials and for instructions. The group timing technique provides production data that is very different from work sampling. It is suggested that this technique can be used to validate estimating data regarding cycle times. It is also shown how a crew balance index can be determined which will allow the manager to evaluate if the crew size is appropriate for the way the work is being performed. The five‐minute rating is shown to be a quick estimator of the delay time of a crew. It is shown that the reliability of the five‐minute rating is not as good as that of work sampling of group timing technique. Various parameters are calculated throughout, and it is suggested that over a period of time, these can be used to monitor crew performance.

Labor has a significant influence on construction productivity. The level of productivity is a result of the driving, induced, and restraining forces acting upon workers. These forces act positively and negatively with regard to productivity improvement. A framework for analyzing fhe influence of each of these forces on four major labor related determinants of construction productivity is presented. Approaches to productivity improvement are analyzed in terms of reducing the negative forces and strengthening the positive forces.

While the timing of payments to the contractor, in the course of the construction process, is an important factor in the project cost, it is not referred to either by the bid‐comparison procedures or by the contract terms, in almost all kinds of contracts used in construction projects. An attempt is made here to overcome the consequent disadvantages to the owner, by means of a procedure based on an obligatory schedule whose activities are appropriately related to the items of the bill of quantities, the whole set‐up forming an integral part of the bid and of the final contract. This enables the owner to prepare cash‐flow estimates for the bids, compare them according to the present value of all expected payments, and select the bid with minimum cost. Apart from this, the procedure neutralizes bid imbalances (regarding unit prices and the production schedule) and facilitates deferment of non‐critical activities, thereby reducing financial cost. The cash‐flow estimate of the winning bid serves as a basis for the owner's budget planning, with much higher accuracy in this function. The suggested procedure is adapted also for comparison of bids in which construction duration is determined by the bidder within a given interval.

A stochastic network model consisting of dependent and independent random variables is developed for construction scheduling. The network model is based on Monte‐Carlo simulation. Data for each network activity consist of a time distribution for the activity under optimal conditions and a series of time distributions for various problems that may lengthen the activity completion time. Dependencies between network activities may be modelled; also, time dependencies for a network activity may be modelled. The implementation of the model is discussed.